Friction element



RQ lla. BENNETT E'rAl. 2,434,532

March 15, 1949.

FRIGT-ION ELEMENT Filed Jan. 4. 1945 '7 sheets-sheet n March 15',l 1949.R. E BENNET-r am.

Fnc'rlor ELEMENT Filed Jan. 4, 1945 www,

Marh15,1949. R. B'. BENNETT am. 2,464,632.

FRICTION ELEMENT Filed Jan. 4,'-1945 7 kSheets-Sheet; 5

March- 15, 1949. R, B, BENNETT ET AL 2,464,632

FRICTION ELEMENT Filed Jan. 4. .1.945 7 Sheets-Sheet 4' N l fifa/'m7655-Fs. E. BENNETT ETAL FRI CTION ELEMENT R.' B; BENNTT -E'r AL March 15,1949.

FRICTION ELEMENT 7 Sheets-Shea?l 6 Filed Jan'. .4, 1945 w .www

S/vloes Patented Mar. 15, 1949 FRICTION ELEMENT Robert B. Bennett,Detroit, and Ray E. Spokes, Ann Arbor, Mich., assignors to AmericanBrake Shoe Company, Wilmington of Delaware Del., a corporationApplication January 4, 1945, Serial No. 571,276

This invention relates to friction elements of the character which areemployed as brake lin-l ings upon automotive vehicles including trucks,busses, and passenger cars, as well as for clutch facings and the like,and to a method of making such friction elements. i

More particularly, the present invention relates to friction elements ofthe aforesaid character embodying novel bonding agents which afford andimpart desirable and advantageous properties and characteristics to suchfriction elements including improved heat resistance and frictionstability over a wide range of operating temperatures.

In general, the present inventionis concerned in one of its primaryaspects withthe utilization inV friction elements of the aforesaidcharacter of bonding agents composed essentially of sulphurized highlyconjugated vegetable drying oil fatty acid esters such, for example, asthose obtained by the isomerization of soya-bean oil, linseed oil andlike vegetable drying oils composed essentially of fatty acid estershaving eighteen carbon atoms in the chain.

In another aspect, the present invention is concerned'with theutilization in friction elements of bonding agents composed essentiallyof an ester higher than the glyceryl ester of the aforesaid fatty acidshaving eighteen carbon atoms in the chain.

As is well known, the fatty acid content of nat-l urally occurringvegetable drying oils such, for example, as linseed oil, perilla oil,and soya bean oil, is primarily in the form of the glyceryl esters ofvarious unsaturated fatty acids having 18 carbon atoms in the chainincluding linoleic acid (Cisl-13202), and linolenic acid (CiaHsoOz) POS-sessing various degrees of both conjugate and non-conjugateunsaturation.

One characteristic common to many naturally occurring as well assynthetic drying oils, and which is of especial significance insofar asthe use of such oils in or as bonding agents in friction elements isconcerned, is the presence in such oils of a certain number ofconjugated double bonds. These conjugated double bonds are especiallyuseful when such drying oils are used, together with sulphur, in or asbonding agents in friction elements in that they greatly improve theresistposition.

12 Claims. (Cl. `26o- 19) `Thus, for example, heat-polymerized linseedoil, cured by sulphurization, has been utilized heretofore as a bondingagent in friction elements and in certain instances friction controllingor stabilizing agents such, for example, as powdered lead formate,cashew dusts, brass, etc. have been added to such bonding agents toimpart thereto improved friction stability over Widely varying operatingcon-ditions and temperatures.

It has been found that the limited degree of conjugate unsaturationwhich is present in drying oils including certain naturally occurringvegetable drying oils such, for example, as linseed oil and soya beanoil, may be materially increased in various Ways as, for example, byisolatin'g or separating the naturally occurring highconjugated doublebonds present therein into the desired conjugated position. One methodof accomplishing this result is disclosed in United States Patent No.2,350,583, which discloses a process of preparing such desirable highlyconjugated oils by isomerizing polyunsaturated higher fatty acids oflinseed oil, soya bean oil, and other vegetable drying oils. The resultof such treatment of any such selected oil is a superior syntheticbonding oil containing a relatively large number of conjugated doublebonds an-d the presence of which in the oil We believe to be ad..vantageous for reasons set forth hereinbefore. When such synthetichighly conjugated oils are used in or as bonding agents in frictionelements the resulting friction elements possess novel and advantageouscharacteristics not possessed by prior art friction elements embodyin-gsimilar or comparable bonding agents including greater heat resistanceof the bond and more uniform friction stability of the resultingfriction elements under Widely differing operating conditions and over aWide range of operating temperatures.

In the present invention We have found, however, that the heatresistance of otherwise coinparable sulphurized drying oils employed inor as bonding agents in friction elements is directly proportional tothe degree of conjugation or conjugate unsaturation in such oils whenoils possessing equal degrees of total, that is, both conjugate andnon-conjugate, unsaturation are compared, Stated otherwise, the heatresistance of such sulphurized oils having corresponding -degrees oitotal unsaturation increases directly With the increase in the number orpercentage of conjugated double bonds in the oil and, conversely, theheat resistance of such sulphurized oils decreases directly with thedegree of conjugation thereof.

By the term comparable as used herein, we

mean conjugated drying oils in which other variable factors are of thesame general orde-r so that the heat resistance of the sulphurized oilscompared is directly attributable to the degree of conjugation therein,and not to other variable Y factors including degree of totalunsaturation, percentage of sulphur in the oil, the extent of the heattreatment to which the oil has been subjected in the curing process,.the extent of exposure to-oxygen, and other variable factors.

We have found, further, that in order to obtain the best results in theuse of such drying oils as bonding agents in friction elements, and thegreatest degree of heat resistance in friction elements bonded with suchsulphurized oils, it is essential not only that the selected bonding oilhave a minimum degree of conjugation but also that the totalunsaturation thereof be maintained Within certain definite limits whichwill be set forth hereinafter. This is for the reason that if the totaldegree of unsaturation in the selected bonding oil is too high the oilWill be unsatisfactory because lacking suicient heat ree sistancewhereas, on the other hand, if the total degree of unsaturation in ltheoil is too loW, it is impossible to sulphurize the oil suciently toenable it to be employed satisfactorily as a bonding agent in frictionelements.

Thus, for example, China-Wood oil while more highly conjugated than atypical bonding oil which may be employed as a bonding agent in frictionelements in the practice of the present invention, and to whichreference will be made hereinafter, is nevertheless inferior to such oilin heat resistance because it is too highly unsaturated. On the otherhand, if cottonseed oil were processed so as to impart to it a degree orpercentage of conjugation which is above the minimumdegree Which We havefound to be essential, in the use of ,bonding oils in friction elementsin the practice of the present invention, it

would still not be a satisfactory bonding oil for use in frictionelements because the degree vor percentage vof total (conjugate and`nonconjue gate) unsaturation present in cottonseed oil is too low to.enable it vto be satisfactorily cured by sulphurization.

More specifically, in the present invention We have ascertained thatfriction elements having the desirable advantages and characteristicsherein referred to, includingsigniflcantly greater heat resistance andfriction stability, over a Wide range of operating conditions, areobtained `by employing in or as bonding agents in such friction elementshighly conjugated drying oils composed essentially of unsaturated fattyacids having 18 carbon atoms in the chain as their glyceryl or otheresters herein named, and in which the extent or degree of conjugation isnot substantially less than 27.5 per cent of total conjugate andnonconjugate unsaturation of the oil, and in which the total degree ofboth conjugate and nonconjugate unsaturation is not substantially lessthan that possessed by an .oil having a total or Woburn iodine number of125 and not substantially more than that possessed by an .oil

d having a total or Woburn iodine number of 180.

Moreover, We have found that not only must oils which are to be used inor as bonding agents in friction elements possess at least the minimumdegree of conjugation and a degree of total unsaturation within thelimits hereinbefore specined but the necessary minimum degree ofconjugation and a degree of total unsaturation within the requiredlimits hereinbefore specified must be afforded primarily and essentiallyby unsaturated fatty acid esters having 18 carbon atoms in the chainrather than by unsaturated fatty acid esters having less than 18 carbonatoms in `the chain, such as the esters of palmitoleic acid(Cisl-33002), or the esters of other unsaturated fatty acids whichcontain in excess of 18 carbon atoms in the chain, such as the esters ofarachidonic acid (Ciel-B202) and the esters of clupanodenic acid(Cal-13602).

While the so-called diene value method has been used heretofore fordirectly measuring the degree of conjugation in oils (see article byGeorge W. Priest et al. in the Journal of Industrial and EngineeringChemistry, vol. 32, No. 10, pages 1314 to 1319, inclusive (1940)), Webelieve that the degree of conjugation of an oil may be moreaccuratelydetermined by employing a combination of Wijs iodine titrationmethod, which is a measure of the degree of nonconjugated un saturationin an oil, and the Woburn iodine titration method, which isa measure ofthe total degree of both conjugated and nonconjugated unsaturation in anoil. (See article by J. D. von Mikusch et al., Journal of Industrial andEngineering Chemistry, analytical edition, vol. 13, No. 11, pages 782 to789, inclusive.) Hence, by sub--V tracting the results obtained by theuse of Wijs method from those obtained by the use of the Woburn methodthe per cent rof conjugate unsaturation in an oil tested may becalculated.

Thus, for example, lin the `case of a typical specimen .of an oil thepercentage of conjugate unsaturation relative to the-total conjugate andnonconjugate unsaturation in the oil was de termined as follows:

(1) The iodine number of the oil by Wijs method, indicating the degreeof non-conjugate unsaturation, vvasY (2') The iodine number ofthe oil bythe Wol burn method, indicating vthe degree of both lconjugate andnoneconjugate unsaturation, was 233 '75/2-33=32.3 per cent conjugateunsaturation in the oil.

Moreover, it vvill be appreciated Ithat in de.`

termining thel Adegree of conjugation and the amount of .totalunsaturation in `an oil according to the methods herein referred to, orotherw1se,

certain limited variations from the limits herein friction elements maybe imparted to or affordedy in selected naturally occurring or syntheticdrying oils of either animalgoryegetable origin by other methods inadditionto the alkali isomerization process which is disclosed in theaforesaid U. S. Patent No. 2,350,583.v Among such addi-4 tional methodsfor imparting the desiredminimum degree of conjugation to a selected oilor oils are the following: (a) separating from theI other components ofsuch an oil, by distillation, the conjugated unsaturated fatty acids orunsaturated fatty acid esters component of the oil having the desiredaforesaid minimum degree of conjugation and the required degree of totalunsaturation within the limits hereinbefore specified; (b) separatingthe polymer fraction from the unpolymerized monomer fraction ofsufficiently heat-polymerized naturally occurring vegetable drying oilsby treatment with acetone or othei` solvent. Thus, as one phase of thepresent invention we have found that by utilizing the polymer fractionof sufficiently heat-polymerized vegetable drying oils, such as linseedoil, we are able to obtain a bonding oil having in excess of the minimumdegree of conjugation and having a degree of total unsaturation withinthe limits herein specified; (c) by dehydration of the polyhydroxyunsaturated fatty acids or unsaturated fatty acid esters present innaturally occurring oils and in certain synthetic oils; and (d) bydehydrogenation of the unsaturated fatty acids or unsaturated fatty acidesters of such oils by the halogenation-dehydrohalogenation process,catalytic removal of hydrogen, or otherwise.

Thus, we have found that the isomerizedy glyceryl esters and theisomerized pentaerythrityl esters of highly conjugated fatty acids whichmay be obtained from linseed oil or soya bean oil by the alkaliisomerization process of the aforesaid Patent No. 2,350,583, orotherwise, afford suitable bonding oils for usein the practice of thepresent invention since such oils have a relatively high degree ofconjugation well above the necessary minimumherein specified while, atthe same time, having a degree of total unsaturation within thenecessary limits hereinbefore specied.

We have also found that the oils of the present invention may beadvantageously employed together with heretofore known oil-modifiedresins, and also as the oil component in oil-modified resins, in or asbonding agents in friction elements for the purpose of impartingdesirable characteristics including increased heat resistance to suchfriction elements. f

Another object of the present invention is to afford new and improvedfriction elements for use upon trucks, busses, passenger cars and thelike and embodying the bonds of the present invention possessingsuperior friction characteristics including greater heat resistance inthe bond and superior friction stability over widely varying operatingconditions and temperatures.

A further object of the invention is to afford a novel method of makingfriction elements, asherein described.l g l.

'An additional object of the present invention is to provide noveloil-modified resins for use as, or as a part of, the bonding agent infriction elements.

A further `object of the present invention is to provide new andimproved friction elements embodying the aforesaid novel oil-modifiedresins of the present invention.

Other. and further objects of the present invention will be .apparentfrom the following description' and claims and by reference to the.

accompanying drawings. Other embodiments of the invention embodying thesame or equivalent principles may be used and changes may be made asdesired by those skilled in lthe art without departing from the presentinvention and the purview of the appended claims.

-A typical formula which has been and may be followed in making frictionelements according to the practice of the present invention, employingas a bonding agent synthetic highly coniugated isomerized linseed oilfatty acid esters having eighteen carbon atoms in the chain, having asuitable acid number and viscosity, and having the necessary minimumdegree of conjugation and a -degree of total unsaturation within thelimits hereinbefore specied, is shown in the following example in whichall parts indicated are by weight:

EXAMPLE 1 Parts by weight Friction material (asbestos) 60.00 Bondingagent (glyceryl esters of isomerized linseed oil fatty acids having 18carbon atoms in the chain and having a viscosity of 800 poises atatmospheric temperature and an acid number of about 2.0) 12.75 Sulphur2.25 Barytes 25.00 Solvent (petroleum naphtha) 7.00

-A typical specimen of the oil referred to in that foregoing Example 1upon analysis 4was shown to possess approximately 29 per centconjugation which is somewhat in excess of the minimum degree ofconjugation essential to an oil in the practice of the presentinvention. The same oil had a Woburn or total iodine number 4of 178.8and hence came within the limits hereinbefore specified for the totalunsaturation of an oil useful in the practice of the present invention.

A typical formula which has been and may be followed in making frictionelements according to the present invention employing as a bonding agenta synthetic bonding oil which is composed essentially of thepentaerythrityl esters of isomerized linseed oil unsaturated fatty acidshaving eighteen carbon atoms in the chain and havinga suitable acidnumber and viscosity, is shown in the following example in which allparts indicated by weight:

EXAMPLE 2 v Parts by weight Friction material (asbestos) 60.00 Bondingagent (pentaerythrityl vesters of highly conjugated isomerized linseedoil fatty acids having 18 carbon atoms in the chain and having aviscosity of 600 poises at atmospheric temperatures and an acid numberof about 6.0) 12,75 Sulphur 2.25 Barytes 25.00 1Solvent (petroleumnaphtha) 7.00

A vtypical specimen of the :preferred :bonding oil yreferred to in theforegoing Example 2 Was 32.6 per cent conjugated and had a Woburn iodinenumber of 176. Hence, this oil possessedadegrec of conjugation inexcessof thelrequire'd minimum degree of conjugationhereinbefore set forth andit also possessed 1a degree `of total unsaturation within the limitsofthe,l present invention.

It Wilibe understood, hovvever,'that in the practice of the presentinvention thefsame t'ypev of oil/ as Wasemployed in 'Example 2, or otherbonding oilshaving higher Vdegrees vof conjugation, may be employed asbonding oils in friction elements in the .practice of the presentinvention provided the degree of total unsaturation present in fsu'ch'selected oil or oils is Within the limits hereinbefore specied.

'A suitable formula which Vmay-'be followed -fin the practice of thepresent-invention, employing as a bonding agent in friction elements,the polymer fraction of a selected heat-polymerized drying oil composedessentially of the heatpolymerized fraction of unsaturated fatty 'acidshaving i8 carbon atoms in the'chain andhavin'g in excess of thenecessary'minimum vdegree of conjugation and possessing a ydegreeoftotal unsaturation within thelimits herein specified, is shown vin thefollowing example in which all parts indicated are by Weight:

EXAMPLE v3 Parts by Weight Friction material (asbestos) 60.00 Bondingagent (polymer fraction of heatpolymerized linseed oil bodied in vacuumand substantially free of lacetone-soluble or u -npolymerized monomerfraction. This oil had a viscosity of 1000poises at atmospherictemperature, an-acid num- `Typical specimens of the'bonding oilsreferred to in the foregoing Examples Sandel were-'271.5 per centconjugatedland hadaWobu'rn iodine number of 143.6.

In the practice of thev present invention We may employ any of ltheheretofore known oil-modified resins with and in place of a part `ofanyofthe bonding oils referred to in the foregoing Examples 1 to 4,inclusive,` for thepurpose of increasing the heat resistance of theresulting bond, orwe may employ an loil-modified resin in Whichfthe oilcomponent thereof is an oil of'the'pres'ent invention. In eitherof suchVinstances the'oil component and the oil-modified resin component of thebond are preferably mixed in aboutfeqil'al proportions and whenyemploying anoil offthe75 (iii present invention as -theoil-modified'resin com iponent'of thebondepreferablyA consists of about40.fper2cent2ofphenoiicresin-and about-60 per cent of an oil of thepresent invention reacted vtogether any suitable-manner such asaccording to 'a typical' process -Which Iwill now bedescribed.

`A typical process which may be employed in preparing an'oil-modiedresin having as the -oil component thereof anf-oil `of Athe presentinven- 'tion 'is Y vsei; 'forth 1int1'ie following example:

Exlliirrm 5 1600 "parts fofp-terti'ary-amyl ,phenol were mixed withl1`53parts, lby Weight, or 37.6 formaldehyde 'andlthe mixture fwasfheatedI-toreflux of 105 C. on -an oil bath'h'avingfatemperature of 130 C. 27.8"parts, by `"Weight(of "l5 N-sulphuric acid was thenrunintothelmiXture-fast enough to enable the refluxing to be continuedwithout outside heating. fThe-'m'ixturethus prepared was then furtherreiiuxe'd'ffor 6x5 hmirsneutralized with lO'per cent caustic`soda,washed with v100 parts of @waterby 'deca-ntation and dehydrated ona metal bathat 200 "C. 4until the cold viscosity of Itheresulting'res'infreached 2000 poises at 25| C. One partQbyweightfof theresin thus prepared was heated in a -suitable vessel with 2 parts, byWeight, f'an oil ofthe present invention, namely, thepentaerythrityl'ester of isomerized linseed oil unsaturated fatty'acidshaving a viscosity or body known as No. Z. "The vessel was heated on ametal 4bath at atemperature of from 225 C. to 250` C. for a periodlof'2.'5 hours, and the oil-resin mixture vtherein"Was-stirred duringthe heating operation. The resulting product was an oil modiedplienolicresin'in which the oil component is an oilof the presentinvention and possessed vaviscosity `of 20,000 poisesat 25 C. Itwillfbe"understoodfin'this connection, that the viscosity'of: the new'oil-'modified resin prepared inthe manner-set forth'above, or in anyother suitable mannerjdepends upon the temperature to which, and thetime during which, the oil-resin mixture is lheated 'during theoperation of preparing' the newcilemodicd resin.

vA suitablecomposition which may be employedin'preparingfrictionelements employing as a bond therein'anV oil'andanoil-modied resin f the present invention is shown in the following"example in"which'al1parts .indicated yare by weight:

- EXAMPLE 6` Parts by weight f Friction materiel (asbestos) 60.00

Bonding agent:

(d) P'entaerythrityl esters of highly conjugated `isom'erized linseedoil fatty acidshaving 18 carbon atoms 'in thech'ain and'having aviscosity of 600 `poises, atatmospheric tempera- Atures and `anacidnumber of about It Will-be '-no'td f that :the com-position set "forth nthe foregoing Example-"f6is similar- 'tothe' therefrom in that in thatapproximately half of the bonding oil in the composition set forth inExample 2 is replaced by an oil-modified phenolic resin having as theoil component thereof an oil of the present invention, said oil-modifiedresin being a product lof .the process described in Example 5. j

Another composition which may be employed in preparing friction elements.according togthe present invention is lthat which is shown in thefollowing example in which all parts indicated are by weight:

EXAMPLE'Y Parts by weight Friction material (asbestos) -60.00 Bondingagent:

(a) Pentaerythrityl esters of highly conjugated isomerized linseed oilfatty acids having 18 carbon atoms in the `chain and having a viscosityof 600 poises `at atmospheric temperature and an acid number of about6.0 6.35,'. (b) Oil-modified phenolic resin modi- 'i fied withChina-wood oil 6.37 Sulphur 2.25v Barytes 2.5.00 Solvent (petroleumnaphtha) 7.00

It will be noted that the composition which is degree of conjugationofthe oil employed -therein increased and, conversely, the heatresistance of such films decreased directly asthe degree of conjugationof the oil employed decreased, when comparing oils possessing rthe samegeneral degree or per cent of .total unsaturation and when controllingthe lother variable characteristics of such oils, as pointed outhereinbefore.

It was :also found 4that the heat resistance -of such sulphurized oilfilms decreased directly with an increase in the total unsaturation ofthe oil when comparing oils having the same degree of conjugation.

It was further found, and this is an important phase of the presentinvention, that sulphurized oil films composed essentially .of thepent-acrythrityl esters of highly conjugated isomerized linseedv oilfatty acids having 18 carbon atoms m-ade of this oil exhibited thelowest percentage "of volatile material lost during the operation ofcuring the films and the lowest percentage of acetone-soluble productscaused by heat decomset forth in the foregoing Example 7 is similar` tothe composition set forth in Example 6 butV differs therefrom in that inplace of an oil-modiwood cil, has been substituted therefor and saidoil-modified phenolic resin modied with China- '40* quantity, by Weight,of an oil of the 'present invention, :as the bonding agentl in thecomposiwood oil is used with approximately an equal tion which is setforth in Example '7.

The oil-modified phenolic resin modified with China-wood oil which isreferred .to in the forei going Example '7 may be an oil-modified 'resinr such as is disclosed in Byck Patents Nos-'1,590,079

and 1,887,883, or any other suitable loil-modified phenolic resin.

In the development of the present invention a number of heat ltests weremade upon sulphurized oil films of many dierent oils possessingdifferent degrees of conjugated unsaturation. These tests were made bycuring the sulphu-rized -oil lms at elevated temperatures anddetermining the various degrees of heat resistance'lfasi '.2

measured by volatility and development of ace- `ure of the degree ofheat resistance suchv sulphurized oils exhibit when used in or asbonding agents in friction elements. i

As a result yof the foresaid heat tests it was deftermined that there isa direct relationship between the degrees of conjugation in, and theheat resistance possessed by, the comparable drying oil fatty acidesters found useful as bonding agents in `the practice of the presentinvention, other variable factors being kept constant. Thus it was foundthat the heat resistance ,ofj said.,

sulphurized oil films increased directly as the tone-soluble fraction;These tests and thper' position during the vcuring operation. A typical-specimen of such an oil employed showed 32.6

per cent conjugation and had a Woburn iodine number of 176, and hencecame within the requirements :as to minimum degree of conjugation andmaximum and minimum limits of total unsaturation as hereinbefore setforth.

The aforesaid findings were also corroborated .by friction and Weartests on the dynamometer upon specimens of lfriction elements bondedwith z the bonding oil referred to immediately above and upon specimensof friction elements bonded With-a comparable prior art oil. Suchdynamometer and wear tests will be described herefv inafter and .theresults thereof are illustrated inthe graphs shown in Figs. 4 to 8,inclusive, of the drawings.

In making the aforesaid heat tes-ts, sulphurized oillms composed of allof the known naturally occurring and synthetic drying oils of vegetableand 'anima1 origin, which offered any possibilities for commercial use,were tested and the results of said heat tests are shown in thefollowing Tables 1, 2, 3, 4 and 5, as Well as in the graphs illustratedin Figs. 1, 2 and 3 of the drawings and which illustrate graphically thedata shown in the aforesaid tables:

Table 1 Sulphurized Film Composed of Oil A Oil B Oil C (1) Percentage ofAcetone-Soluble Material Formed In Film During Preliminary CuringOperation 5. 94 6. 80 8. B0

After Further Curing Film 1 yHour at 315 C'.

4 (2) Percentage Volatile Material Lost" 2.61 3. 86 14. 9

(3) Percentage Acetone-Soluble Material Formed l0. 4 11.8 30, 3 (4)Total Percentage of Weight of Film After Curing Film One Additional Hourat 350 C.

(5) Percentage Acetone-Soluble Material Formed 5. 91 12.0 31, o (6)Percentage Volatile Material Lost.. 1.01 2. 68 21. 7 (7) PercentageConjugation in Oil 32. 6 29. 9 30. 4 (8) Woburn Iodine Number of Oil(Total Unsaturation) 176 178, 8 18'4, 4 (9) Acid Number of Oil 4. 9 2.1.5, 2 (A10) Viscosity of Oil in DOSeS at 25 C. 534 540 435 Table? 2*Sulphurized Film'Composed of; OilD y1011.111' v 011B" LOiIG -OilH- f0111i oilJ.' 011K 0711,

(1)'Percent`age'ofA`ceto1ie=SolubleMaterial Fornidil Filni l DuringPreliminary Curing Operation 0. 75 y 14:7y` 12.7 18. Ell 10.9 15.8` 13.320.0 17.7

After Furth' Curin'g 'Film1 Hour at 315 C.

(2) Per 'ntag'evolatile Material Lost 4.48 1 7125;" 8.03y I 1110 8.309.42' 13.15` 5;.52 15,0 (3) Percentage Acetoii'eSoluble MaterialFormed'. 19.5 25101 2913! v 21.3 27.1 2316 39.2V 31. 6. 30.0 (4)TotalP-ercentageoiWeightof-Fllm Lost Y.. 30.73 46.95- 5003 51.1 56.358.82 60.165 60,12 62,7

After Curing Filn One Additional Hour at 350 C'.

(5) Percentage Acetone-Soluble Material Formed (6)- Per'cetag VolatileMaterial Lost (7) Percentage Conjugationin Oil..

(8)' Woburn Iodine Number of Oil (Total Unsaturation) 9) Acid Number ofOil.. ..1

(10) Viscosity of Oil in poises at 25 C Oil C Oil D (1) Percentage ofAcetonelSoluble Material Formedinfilm Duringl lreliminar'y Curing A v gOperation. 6. 94v 6. 80 8.80 6. 75

After Further Curing Fz'm I- Hourat 315 C'.

(2) Percentage- Voi'atiie Materiai- Y l LOSt. 2. 3.86 14.9 4.48

is.: rsi 51.0: 30.15

Afm curing Film1 Additional Hour at 360 C'.

(5) Percentage Aceton-Soluble .A w 7 lMaterial Formed.. 5:01 12.00 31.0(6) Percentage Volet l Lost. 1.01 l 2.68 y 2`1.7: 32.6? 29.9 i 10.4A21.5 (8) Wo urn Iod Oil Total Unsaturatiou) 175 178.8 l lnL 143.6 (o)Acli; Number of 011 oo 1 2.1 1 5.2. 1.o (10) Viscosity of Oil In 25 C534'j f 540' 435 1340 Table 4 Group 1 Group 2 Sulphrized Film Composedoi Oil-E Oil-F Oilf G Oil H Y OilI Oil J Oil K Oil L (1) Perentageoiacetone-Soluble Material Formed in Film During v, l

Preliminary Curing Operatiomas.. v v l'. 7 12. 7' 18.8 10.0 15.8 13. 320.0 17.7

After Furher Curing I Hour at 315 C.

(a) PercentageVolatiieMatei-iellLost 7.25l 8.04 11.0 S236 9.42' 8.158.52 15.0 (3) Percentage',Acetone-Soluble Material Formed `29.33 21.327.1 23.6 39.2 31.6 30.0 (4) Total Percentage of Weight of Film Lost...46.95 50.03 51.1l 56.3 58.82 v60.65 00.12 02.7

After Curing Fitm 1 Additional Hour at 350 C'.

(5) Percentage Ac'etoue'-Soluble Material Formed Table v Pair 1 Pair 2Pair 3 Oil M Oil N Oil O Oil P Oil Q Oil R (Glyceryl (P. E. (Glyceryl(P. E. (Glyceryl (P. E.

, Sulphurlzed Oil Film Composed of Ester) Ester) Ester) Ester) Ester)Ester) (1) Percentage of Acetone-Soluble Material Formed in Film DuringPreliminary Curing Operation 6.80 5.94 20.0 14. 6 17. 5 17. 2

After Further Curing] Film 1 Hour at 315 G'.

(2) Percentage Volatile Material Lost 3. 86 2. 61 8. 52 7. 98 18.0 7. 07(3) rPercentage Acetone-Soluble Material Formed. ll. 8 10.4 31. 16. 428. 9 25. 4 (4) Total Percentage of Weight of Film Lost.. v 22. 46 18.95 60. 12 28. 98 64. 4 49. 67

After Curing Film 1 Additional Hour at 350 C.

(l5) Percentage .acetone-Soluble Material Formed 12.00 5. 91 30. 00 19.7

, (6) Percentage Volatile Material Lost. 2. 68 1.01 15.0 3. 40 (7)Percentage of Conjugation in Oil 29. 9 32.6 14.6 14. 5 l0 25. 2 (8)Woburn Iodine No. of Oil... 178. 8 176.0 139.4 138.0 118 117. 8 (9) AcidNumber of Oil 2.1 4. 9 1.76 2. 63 4.0 4. 20 (10) Viscosity of Oil inpoises at 25 C- 540 534 800 840 833 580 List of ozls referred to inTables 1 to 5, inclusive Designation Description or Name of Oil (AllDerived From of OilIn -Unsaturated Fatty Acids Having 18 Carbon TablesAtoms in the Chain) Pentaerythrltyl Esters of Isomerized linseed oilunsaturated fatty acids.

Glyceride-Esters of Isomerzed linseed orl unset` urated fatty acids.

Oiticica Oil.

substantially free of acetone-soluble unpolymerized or monomer fraction.

Dehydrated castor oil. l

A modified vegetable drying oil.

Dehydrated castor oil.

A modified vegetable drying oil.

Modified fish oil.

Purely polymerized linseed oil.

Modified sh oil.

Glyceryl esters of isomerized linseed oil unsaturated fatty acids.

Pentaerythrityl esters of lsomerxzed linseed oil unsaturated fattyacids.

Purely polymerized linseed oil.

Pentaerythritol liuate.

Glyeryl esters oi soya. bean oil unsaturated fatty ac s. Pentaerythritylesters of soya bean oil unsaturated fatty acids In preparing thesulphurlzed oil films all of the oils referred to in the foregoing listwere employed as oils bodied to a viscosity above 400 poises at C.

The foregoing Tables 1 and 2 show theA relationship between the heatresistance of the sulphurized oil films .tested and the comparativepercentages of conjugation present in the oils employed in making thesulphurized oil films tested.

As may be seen by reference to Table 1 the sulphurized oil lms referredto therein were composed of oils having at least the necessary mini-Vmum percentage of conjugation required in the practice of the presentinvention, with other variable factors including the degree of totalunsaturation being of the same general order. Certain of -the oilsemployed in making the sulphurized oil lms referred to in Table 1,namely, oils A and B, also possessed a degree of total unsaturation fwithin the limits required in the practice of the present inventionwhereas the degree of total unsaturation possessed by oil C was inexcess of the hereinafter, (oil D) the oils employed in making thesulphurized oil films tested, and the results Polymer fraction of heatpolymerized linseed oil of the same general order.

of which are referred to in Table 2, possessed a. degree of conjugationbelow the minimum required of an oil in the practice of the presentinvention, other variable factors including the degree of totalunsaturation being of the general order.

Thus by comparing the total heat losses of the sulphurized oil filmstested, as shown in horizontal row 4 of Tables 1 and 2 the superior heatresistance of the sulphurized oil films composed of otherwisesatisfactory oils, having at least the minimum degree of conjugationrequired in an oil to enable it to be used in the practice of thepresent invention, may be seen.

Tables 3 and 4 show the relationship between the degree of totalunsaturation in the oils employed in making the sulphurized oil filmstested and the comparative degrees of heat resistance possessed by saidfilms, other variable factors in such oils, including percentage ofconjugation, being of the same general order.

By reference to Table 3 it Will be noted that the sulphurized oil filmsreferred to in this table were composed of oils which possessed at leastthe minimum degree of conjugation required of an oil to enable it to beused in the practice of the present invention and all of the oilsreferred to in Table 3 except one (oil C) contained a. degree of totalunsaturation within the limits hereinbefore specied. The varying degreesof total unsaturation of all of the oils referred to in Table 3 were ofthe same general order as were other variable factors.

Table 4 contains significant data compiled from the aforesaid heat testsupon sulphurized oil films composed of oils having a. degree of totalunsaturation within the limits required in the practice of the presentinvention but rall of which oils except one, namely, oil L, contained adegree or percentage of conjugation below the minimum degree ofconjugation hereinbefore specified. The degree of total unsaturation ofthe oils referred to in Table 4, and other variable factors of the oilsreferred to in this table, were In order better to show the relationshipbetween heat resistance and degree of total unsaturation the oilsreferred to in Table 4 are divided into two groups 1 and 2 each`composed of oils having degrees of conjugation and total unsaturationof the same general order with the exception of oil L hereinbeforereferred to.

The data in Table 5 shows the superior heat resistance of sulphurizedoil films composed of the pentaerythrityl esters of unsaturated fattyacids having 18 carbon atoms in the chain overY the glyceryl esters ofthe same fatty acids, as revealed by certain of the heat tests uponsulphurized oil lms hereinbefore referred to. In order to show thecomparative degrees of heat resistance possessed by the sulphurized filmtests vthe oils referred to in Table 5 are arranged in `three pairs,each pair consisting of an oil composed ofthe glyceryl esters ofunsaturated fatty acids having 18 carbon atoms in the chain and an oilcomposed of the pentaerythrityl esters of the same unsaturated fattyacids.

The data shown in numbered horizontal row 1 in Tables l to 5, inclusive,were compiled from analyses of sulphurized oil films cured during aiiiteen hour cycle progressively increasing temperatures of from 80 C.to 170 C. The thus cured sulphurized iilms were then further sub-4jected to heat at a temperature oi 315 C. for a period of one hour,whereupon specimens of the thus heated llms were tested to determine (a)the percentage of volatile material lost as a result of the heatingoperation, and (b) the percentage of acetone-soluble products of heatdecomposition formed in the lms as a result of the heating operation.These data are shown in numbered horizontal row (2) and in numberedhorizontal row (3), respectively, in the tables.

The total percentage of the weight of each sulphurized oil nlm lostduring both the aforesaid preliminary curing operation and during thesubsequent heating operation at 315 C. is

shown in numbered horizontal row (4) in the tables.

The thus cured sulphurized oil ilms were thereupon heat treated anadditional hour at a higher temperature of 350 C., whereupon the filmswere again tested to determine the percentages of acetone-solubleproducts of heat decomposition formed in the films, and the percentageof the weight of each Film lost in the form of volatile matter formed asa result of the curing operation at 350 C. These data are shown innumbered horizontal rows (5) and (6), respectively, in the tables.

The data in numbered horizontal row (7) in each of the tables show thedegree of conjugation in each of the oils employed in making the'sulphurized oil films tested, as expressed in terms of percentage ofconjugate unsaturation present T in the oils relative to the totaldegree of both conjugate and nonconjugate unsaturation, as hereinbeforedescribed. y

The data in numbered horizontal row (8) in the tables show the Woburniodine number of each of the oils employed in making the sulphurized oiliilms tested, thus indicating the comparative degrees of totalunsaturation in the oils employed in making the films. The data innumbered horizontal row (9) in the tables show the acid number of theoils employed in making the 'sulphurized oil films tested, and the. datain numbered row (10) oi each oi the tables 'show the viscosities of saidoils in terms of poises at 25 C.

By reference to the oils referred to in Table 1 it will be noted thatthese oils, namely, oils A, B and C, all possessed a .relatively highdegree of total unsaturation, as indicated by their Woburn iodinenumbers of 176, 178.8 and 184.4, respectively.

On the other hand, with one kexception (oil L), -all 'of the oilsreferred to in Table 2, namely, oils D, F, G, H, I, J and K had arelatively lovv degree of total unsaturation, as shown by 160.6, 139.4,138.2, 150.6 vand 139.4, respectively. However, only one of the oils inTable 2, namely, oil D, had the necessary minimum degree of conjugationherein specified.

By reference to numbered horizontal row (4) in Table 1 it will be notedthat the total percentagesnor" the weights of the sulphurized oil filmscomposed of oils A and B which 1vere lost during the preliminary curingoperation and during the ensuing 'curing operation at 315 C. were 18.59per cent and 22.46 per cent, respectively. These losses wereinversely'related to the degrees of conjugation in the respective oils,namely, 32.6 per cent and l29.9 per cent, respectively, (horizontal row7 in Table 1)', in oils having the same general degree of totalunsaturation as' shown by their Woburn iodine numbers of 176 and 178.8,respectively, (horizontal roW 8 in Table 1). Oil A was composedessentially of the pentaerythrltyl esters of isomer-ized unsaturatedlinseed oil fatty acids having 1S carbon atoms in the `chainA and oil Bwas composed essentially of the glyceride esters of isomerizedunsaturated .linseedfoil fatty acids having 1S carbon atoms in thechain.

However, upon reference to the Ydata in Table 1 showing the results ofthe tests made upon sulphurized oil films composed of oil C (oiticicaoil) it will be noted (horizontal roW 4) that the total percentage ofthe weight of the lm lost during the preliminary .curing operation andduring the subsequent curing operation at 315 C. (54.0 per cent) wasapproximately three times as great as that of the nlm composed of oil A(18.59 .per cent) and approximately two and a half times as Lgreat asthat of the film composed of oil B (22.46 per cent), even though thevariation in the percentage of conjugation in the three oils (A, B andC) was relatively very small (32.6, 29.9 and 30.4 per cent,respectively, see horizontal row 7 in Table 1) The explanation of thisphenomenon resides in the i act that even though the degree ofconjugation in oil C (30.4 per cent, see horizontal row 7 in Table 1)was above the minimum degree of conjugation hereinbefore specified, (notsubstantial-ly less than 27.5) the degree of total unsaturation in oil CWas too great to impart to the ilm composed of thatoil the heatresistance .possessed by those oils which are useful as bonding agentsin friction elements in the practice of the present invention. Thus byreference to horizontal row 8 in Table l it will be noted that theWoburn iodine number of oil C Was 184.4 and hence the degree of totalunsaturation of this oil, as measured by its Woburn iodine number, wassubstantially greater than the maximum permissible `upper limit of totalunsaturation in an oil which may be used in or as a bonding agent infriction elements in the practice of the present invention, namely,l anoil having a Woburn iodine number not substantially in excess o f 180.`

All but one of the oils (oil D) in Table 2 possessed percentages ofconjugation below the minimum of not substantially` less than 27.5`hereinbefore specified (see horizontal row 7 in Table 2), and all butone of the sulphurized oil lms made from the cils in this group (thefilm made from `oil D) exhibited unsatisfactorily high percentages(horizontal row 8 in Table 8) Within the `limits herein specified. ,Y

:Oil :DrinTable 2 -was composed of the polymer fraction of aheat-polymerized linseed oil substantially free of acetone-solubleunpolymerized or'monomer fraction ofthe original oil. As shown in Table2, a sulphurized lm made from oil D showe yda total heat loss of 30.73per cent, which was lcomparable tothe total heat losses of sulphurizedfilms made from oils A and B in Table 1, `rather than to the heat'lossesof sulphurized films :made from oil C in Table 1 and roils F to L,inclusive, in Table 2. This was due to the fact that oil D contained therequisite minimum degree of conjugation required in the practice of zthepresent invention, namely, 27.5 per cent, and it also possessed therequisite amount of total unsaturation herein specified as indicated byits 'Woburn iodine number of 143.6.

Oils E, F, H, andI were oils in which the degree of conjugation in theoil had been increased by la process of dehydration lor dehydroxylationand are further identified in thelist of oils referred :to in theforegoing Tables 1 to 5, inclusive,

whereas oil K was a purely polymerized linseed oil. Hence, it will beseen from Tables 1 and'2 that'l 4in otherwise comparable oils havingcomparable degrees of total unsaturation within the 'limits hereinspecified, the heat resistance of sulphur- 'ized oil films made fromsuch oils increases directly with an increase in the degree of conjuga-'tion'inthe oil and, conversely, decreases directly with .a decrease intherdegree of conjugation in 'such Voil (compare oils A, Band C in Table1 and oils D to K, inclusive, in Table 2).

to or above the minimum of 27.5 per cent herein specified, but that thedegree of total unsaturation in an oil possessing the requisitepercentage of conjugation be "maintained within the limits .of totalunsaturation herein specified.

't will be noted by reference to Table 2 that lthe sulphurized oil lmcomposed of oil L (which was a fish oil) showed an unsatisfactory veryhightotal loss of 62.7 per cent of its initial weight after lthecompletion of the preliminary curing operation and the subsequentheating operations at 315 C. and 350 C. (see horizontal row 4 in Table2)notwithstanding the fact that the degree of total unsaturation in thisoil, as shown Jfound that not only must oils which are to be 'used inoras bonding agents iniriiction elements 'possess at least the minimumdegree of conjugaftion and a degree of total unsaturation within thelimits he-reinbefore specified but-the neces- '.saryntiniminn degreeofconjugation and a del'gres of vtotal unsaturation within the requiredelimits hereinbeforespecied must be afforded Vprimarily and essentiallyby unsaturad lfatty acid esters having 18 carbon atoms in the chain,rather than by vunsaturated fatty acidv esters -having less'than `V18carbon atoms 4inthe chain,

such as the esters of palmitoleic acid (CiaHsoQz) .or Athe esters ofother unsaturated vfatty .acids .whichfciontain .in excess Vof ,18carbon atoms in the chain, such 'as the estersof arachidonic acid'(CzoHazOz) and the esters of clupanodonic acid '(C22H36O2). f

Thus, oil L was a sh oil containing a relatively large percentage ofesters of saturated fatty acids of the CnHanOz type and relatively largev percentages of esters of palmitoleic acid (Cisl-R002), and 0iarachidone acid (C2oH3202) and of clupanodonic acid (Cm-13602). We foundthat an oii composed primarily of esters of such unsaturated fatty acidsare not satisfactory for us-e in the present invention even though thepercentages of conjugation and the degree of total unsaturation in suchoil came within the limits herein specified. Hence we have found that itis essential to the present invention that the desired minimum degree ofconjugation and the required degree of total unsaturation hereinspecified be afforded by an oil or oils composed 'essentially of estersof unsaturated fatty acids having 18 carbo-n atoms in the chain. This istrue `of all of the oils referred to in Tables 1 to 5, inclusive, exceptthe aforesaid oil L.

Tables 3 and 4 contain the same data which are shown in Tables 1 and 2,which have been analyzed hereinbefore, and were compiled from tests uponthe same sulphurized oil lms as are referred to in Tables 1 and 2.However, rather than arranging the sulphurized oil films and thesignificant data relative thereto in two groups, namely, those relatingto oils possessing relatively high and those relating to oils possessingrelatively low degrees of total unsaturation, respectively, as in thecase of the oils referred to in Tables 1 and 2, in Tables 3 and 4, theoils are `grouped into three groups with the oils in each i,grouppossessing corresponding degrees of conjugation.v Thus oils A, B, C andD, which are shown in Table 3 had relatively high percentages ofconjugation of 32.6, 29.9, 30.4 and 27.5, all above the minimum hereinspecified. Group 1 in Table'4, composed of oils E, F, and G hadpercentages of conjugation of 26.5, 25.7 and22.7, all below the minimumherein called for; and group 2 in Table 4, composed of oils H, I, J, Kand L had still lower percentages of conjugation of 19.3, 16.3, 16.1,14.6 and 27.4, all below the minimum required of an oil to enable it tobe used as a bonding oil in friction elements in the practice of thepresent invention (see horizontal row 7 in Table 4).

By comparing the percentages of total loss in weight in the sulphurizedoil lms of each of vthe three ranges, as shown in horizontal row 4 ofTables 3 and 4,'as a result of the preliminary curing operation and as aresult of the further heating operation at 315 C., with the degrees oftotal unsaturation of the oils, 4as shown in horizontal row 8 in Tables3 and 4, it will be observed that `for oils having comparable degrees ofconjugation, the heat resistance of the sulphurized oil lms madetherefrom decreased with an increase in total unsaturation in the oils,

Table 5 illustrates a phase of the present invention hereinbeforepointed out, namely, that -sulphurized oil films composed of thepentaerythrityl esters drying oil fatty acids show greater heatresistance than the glyceryl esters of such drying oil fatty acids, allother variable factors including degree of conjugation and amount oftotal unsaturationl being equal or comparable. Moreover, we have vfoundthat this Ais true even though the percentage of conjugation `in the oilis below the minimum limit herein speci- .,ed Qand'even though theamount of total unsat- 19 uration Ain the oil is outside the limitsherein set forth.

Thus it will be noted by reference to Table that the oils thereinreferred to are arranged in three pairs, with each pair consisting of(l) an oil which is composed essentially of the glyceryl esters ofunsaturated drying oil fatty acids and (2) an oil which is otherwisesimilar to the other oil in the same pair except for the fact that thepentaerythrityl ester has been substituted for the glyceryl ester.

Thus pair 1 in Table 5 consisted of oil M, which was composedessentially of the glyceryl esters of slow drying isomerized unsaturatedlinseed oil fatty acids, and oil N which was composed essentially of thepentaeryt'hrityl esters of fast drying isomerized unsaturated linseedoil fatty acids. Pair 2 in Table 5 consisted of oil O, which wascomposed essentially of a medium drying socalled purely (heat)polymerized natural linseed oil, that is, a heat-polymerized linseed oilcomposed of the -glyceryl esters of unsaturated linseed oil fatty acidscontaining substantially no oxidized oil, and oil P which was an oilotherwise comparable to oil O but in which the pentaerythrityl estershad been substituted for the glyceryl esters of the same unsaturatedfatty acids. Pair 3 in Table 5 (consisted of oil Q, which was lcomposedessentially of the glyoeryl esters of semidrying unsaturated soya oilfatty acids, and oil R which was an oil otherwise similar to oil Q butin which the pentaerythrityl ester had been substituted for the glycerylester vof the same semidrying unsaturated soya oil fatty acids.

It will be noted by reference to the percentages of heat losses shown inhorizontal row 4 of Table 5, and which represent the percentages oftotal loss in weight of the cured sulphurized oil films after thecompletion of the preliminary curing operation and after the subsequentheating operation at 315 C. that the sulphurized films composed of theoils which were essentially pentaerythrityl esters of variousunsaturated fatty acids were in every instance more heat resistant thanthe glyceryl esters of the same fatty acids. Such heat losses are ameasure of the comparative heat resistances of such sulphurized oilsemployed in or as bonding agents in friction elements. Hence we havefound that the pentaerythrityl esters of unsaturated fatty acids are, ingeneral superior for use in or as bonding agents in friction elements tothe glyceryl esters of the corresponding fatty acids.

Certain of the significant data shown in Tables 1 to 5, inclusive, areembodied in the graphs illustrated in Figs. 1, 2 and 3 of the drawings.Thus the relationship between the various degrees of conjugation in theoils referred to in Table 1 and the total heat losses of the Sulphurizedlms referred to in Table 1 are illustrated in graph 4 in Fig. 1, and therelationship between the various percentages of conjugation in the oilsreferred to in Table 2 and the total heat losses of the sulphurized oilfilms referred to in Table 2 are shown in the form of graph 5 in Fig. 1.The ordinates in Fig. 1 represent the total heat losses of thesulphurized lms in percent, as set forth in horizontal row 4 in Tables 1and 2. and the abscissae represent the percentages of conjugation in theoils employed in making the sulphurized oil films, as set forth inhorizontal row 7 in Tables 1 and 2.

The letters A, B and C on graph 4 in Fig. 1 refer to the correspondinglyidentified oils in Table 1 and letters D to L, inclusive, on graph 5 20in Fig. 1 refer to oils D to L, inclusive, respectively in Table 2.

By reference to graph 4 in Fig. 1 it will be noted that the per cent oftotal heat loss of the sulphurized oil lms rose rapidly between points Aand B (oils A and B in Table 1) with a comparatively small decrease inper cent of conjugation.

It is significant to note that there is a very sharp rise in graph 4 inFig. 1 between points B and C (oils B and C in Table 1), indicating amarked increase in per cent of heat loss of the sulphurized oil lms,even though there was a slight increase in percentage of conjugation. Aspointed out hereinbefore, this was due to the fact that the degree oftotal unsaturation (184.4) in oil C (oiticica oil) is above the upperlimit (180.0) hereinbefore specified.

It is also significant to note that there is a very sharp rise in graph5 in Fig. 1 between points D and E (oils D and E in Table 2), indicatinga pronounced increase in per cent of total heat losses of thesulphurized` oil films tested, even though the decrease in percentage ofconjugation between the two oils D and E (27.5 and 26.5) was relativelysmall and represented only a drop of 1 per cent below the critical lowerlimit of percentage of conjugation (27.5) hereinbefore specified.

The more gradual. rise in graph 5 in Fig. 1 between points E and J (oilsE to J, inclusive, in Table 2) illustrates the manner in which thepercent of total heat losses in the sulphurized oil lfilms tested rosewith decreases in the percentages of conjugation of the aforesaid oils Eto J, inclusive; a subsequent slight irregularity being noted betweenpoints J and K on graph 5 in Fig. 1 (oils J and K in Table 2).

The character of that portion of graph 5 in Fig. 1 between points K andL (oils K and L in Table 2) is significant since between these twopoints the per cent of conjugation in the oils rose from 14.6 for oil Kto 27.4 for oil L (horizontal row 7 in Table 2) while, notwithstandingsuch a marked increase in percentage of conjugation (from a point (14.6)far below the minimum herein specied (27.5) to a point (27.4) onlyslightly below said minimum lower limit of percentage of conjugation),there was an increase in the percentage of total heat losses in thesulphurized oil films composed of these oils (K and L) from I60.12 to62.7 (see horizontal row 4 in Table 2) vrather than a decrease inpercentage of total heat losses of the sulphurized oil films as mighthave been expected. As explained hereinbefore, this was due to the factthat oil L wasy a fish oil containing a relatively large percentage ofesters of unsaturated fatty acids having less than or more than 18carbon atoms in the chain and hence this oil is unsatisfactory for usein the practice of the present invention even though it possessed adegree of total unsaturation within the limits herein specified as shownby its Woburn iodine number of 171.1 (see horizontal row 8 in Table 2).

The ordinates in Fig. 2 represent the total heat losses as set forth inhorizontal row 4 of Tables 3 and 4 and the abscissae in this figurerepresent the various degrees of total unsaturation in the oils employedin making the sulphurized oil films tested as indicated by the Woburniodine numbers of said oils which are set forth in horizontal row 8 ofeach of Tables 3 and 4.V y

Thus graph 6 in Fig. 2 illustrates the relation ship between the varyingdegrees of total unlisiituration of 'thefol'sgireferred ito in numeVvstilphurized 4oil films A"tested afs-lsetf'forth iin horizontalfrow 4of 'Table 1-3. Thel'etters D, Baa-nd C 7on this graph `refer 'toIthe'*correspondir'lll identified oils referred to 'in Table i3.

By reference to graph 16 in Fig. "52 it Willbe-note that the percentage:of heat'lossesiin'the isdlp'hur ized oil v.liris tested=increasedrapdly `after the Woburn iodine numbersfof 'the -o'ils :passedthe upper limit of 180 hereinbefore specified, shown by the sharp riseof vgraph v6 `between points 1B and C and between which points fthisgraph crosses Ithe vertical line or :ordinate-which represents 'thepermissible upper :limit of 'ltotal unsaturation hereinbeforefspecie'dandiaszrepresented by a yWoburn iodine nuniberfof 180.

Graphs '7 and "8 in Fig. "-2 'illustrate-.graphically the-data `set"forth in l'ior'izontal Crows 4 fand Stof groups f1 and 12,respectively, "inwablefandxshow howthe ltotal 'heat 'losses of thersulphurize'd 1o`il nlm-s tested variedl directly :with `an finer-easejfin the 'to'tal unsaturation fof the oilsemployed. 'The letters E, FVand fGfongraph -17 refer ltothe@correspondingly identiiied oils 'whichare referred to inrgroup 1 of Table 4 and the letters, H, .FL 5J .andLon graph v8 reierto't'he similarly identidad oils which are :referredto ingroupfz billable-'4.

'In Fig. 13 the 'abscissae represent th/e v.varying percentages of heatlosses in the rsulpliurlzedioil lms 'tested as set for-th 'in horizontalrow in Table '5. Graphs 9 vand 1() iri"Fig.f3`l1u'Strate graphically thedata set forth in `horizontal"rowfi of 'Table 5 4as to pair 1 :of the'sulphurized oi'llms therein referred 'to and show the superior heatresistance of the 'pentaerythrityl v'ester-foils lover the glycerylester'sof't'he same unsaturated fatty acids as shown `by the shorter'lengthf'f .-graph ill) 'as compared to graphe.

Graphs 11 and 12in Fig. 3 'illustrateagrapliically the data setfortlfiin horizontal row 4lo'f Table 5 as vto pair 2 of the sulphurized oilitilmstherein referred'to and yalso show the-'superiorh'eat resistevance-of the pentaerythrityl es'te'riols :over 'the glyceryl esters'o'fthe same unsaturatedifatty'facids :as'shown by thesighiiicantly'shorterlength -of graph 12 as compared to graph 1l.

4Graphs 13 and 14 in Figs illustrategraphically the ydata set forth inhorizontal row ."o'filfa'ble i5 as to pair 3 of the su'l'phurize'd oilfil-ins. therein referred to and further show 'the superior iheatresista-nce of the pentaerythrityl fester-oils *over the .glycerylestersof 'the same unsaturated fatty acids as shownby the shorter lengthofligraph .14

`as vcompared to graph r13.

In making the 'tests,fthe `.results .of-which 'lare shown in the graphsillustrate'dfin'iFigsgXifand:15 of the drawings, 'the specimensfoffsfriction gelem'ents `whichy were employed were Ialll testledzundercontrolled conditions `which wereas nearlidentical as possible; that isto say, all'variablercfactors were 'so vcontrolled .that .the `graphspreflect'.difference 'in friction characteristics imparted 'tothe-friction elements `tested by the Adifferent.sulphurized bonding .oilsemployed therein. Thus 1in makinng 'the tests, 'the Vresults of whicharexillustrated by the graphs in Figs. 4 ande,isidecii'rrens of"friction elements to lle-tested `were 'mounted upon Ythe brake assemblyof an inertiatype'dynomometer operated by controlled "hydraulic linepressure and all lvariable factors, such as Vkinetic energy load on thedynamometenispeed, actuating hydraulic line pressure, volume andtemperature :air :allowed 'tio come into 'contact'wththe-ibrak'eassemblylmade1fsubstantiallyfzconstaritrusoisr 'as Ecs possible-imc onlyivariable being lthe .frequency/of brekeappi ation.Moreoveniinmakin'g'the-'conf trol-led v-te'mpeiiature ffrict'ion tests,"the results of which are illustrated "in the isoli'd vline :graphs 1inFigs. t4 and UA5 of the drawings, the internal Iteniperatures of thefriction elements tested werehe'ld alt .substantially constanttemperatures vWithin a. variation o'fiplusor ininuso F.

`The solid Iline graphs in Figs. 4 and .5, "therefore, 'illustratevariations in friction characteris'tics of lthe friction elements'tested which @are directly -fattributabl'e to the effect of internaltem perature variations upon the 'bonding agents 'oruponvthelbondingfand friction-controlling agents embodied therein.

En 'making the tests, the results o'f which are 'illustrated-inFig's.'=4 and '5, the specimens werezsubjecte'd tto/two fdiieren't typesof tests which will new "be 'briefly Ldescribed. Thus, by reference tothe graphs illustrated in'lFigs. 4fand5 of the drawings, it will "benote'dth'a't the ordinates 'are Yexpressed in 'terms jof poundsactuating pressure per foot per second,'per second, corresponding'itothe 1rate 'of deceler-at'ionA of an -automotive'vehicl'e during a4braking operation,'whereas the fa'bscissae are expressed in timeintervals during which'a predetermined nurnber .'of id'eceleration's orscrcalled stops -at 'various predetermined internal friction elementtemperatures corresponding `vto braking operations in Jan automotivevehicle, were made.

"Thus, the graphs represented'by fthe solid lines in Figs. 4 and 5:representfthe friction characteristics of the friction elements testedat controlled internal lining temperatures and at progressivelyincreased temperaturesteps of '50 F., commencing fat 250`F. 'and'through '500 iF., fifty "Stops T61' decelerations beingv made at 'eachtemperature step, as shown byf-the'abscissae at-the `bottom of Figs. '4and 5.

The dotted "line graphs shown in Figs, 4 'and 5 illustrate the resultsof lsfr-called vfriction recovery tests made upon rthe samelsperiiliiens of friction elements as were :employed 'in making thetest, theresults .ofwhich are represented bythe solid line graphslhTFi'gsAan'd-B ofthe drawings. 'Howeverfin 4the 'case of the dottedline graphs vshown in Figs. 4 and '5, each 'friction'recovery test "Wasmade immediately afterthe lcompletioh of th'epre ceding controlled'temperature test upon the specimen. Each of these so-called frictionrecovery'tests consisted of -ten decelerations or stops,

corresponding tobrak'ing operations 4in an automotive 'vehicle `As"shown iin 'the dotted line graphs in Figs. 4 -al'nd 5, the ten'de'c'eleratio'ns or stops in each frictionrecovery test vwererriadewith a deiinit'e"time interval between each'decelerationI or rstop to'fallow the internal temperature of the friction element 'to decreasefrom the tem.. perature used in the-immediately preceding -controlledtemperature step 'to .a lm'inimun'i initial temperature of the frictionelement of 150^or less; that is, to fa temperature below the .criticaltemperature kofbonding:agents'heretofore used in ized -linseed :oil'containing substantially 'no oxidizedsoil. Thesevwere controly.tests:since friction elements embodying .such :aV 'bonding .agent.have .1

. 23 been knownA and used heretofore. No frictioncontrolling orfriction-stabilizing agent was embodied in the friction elements whichwere employed in making the control tests, the results of which areshown in the graphs illustrated in Fig. 4.

By reference to Fig. 4 it'will be noted that the solid line graphs 15and 17 in the rst two friction tests, made at controlled internal liningtemperatures of 250 F. and 300 F., respectively, are, in general, of ahorizontal pattern with a slight upward trend at the end of each test,showing only a relatively small loss of friction or so-called ffade anda substantially complete recovery. It will also be noted, in thisconnection, that in the two so-called friction recovery tests made atthe relatively low temperatures of 250 F. and 300 F. and the results ofwhich are illustrated by graphs 16 and 18 in Fig. 4, there was verylittle loss of friction or so-called fade However, upon reference to thecontrolled friction internal lining temperature test made at the nexthigher temperature step, namely, 350 F., the results of which areexemplified by graph 19 in Fig. 4, there was a considerable loss offriction-stability or fade during the early part of the test, as shownby the sharp and nearly vertical drop in the graph, with no permanentfriction recovery, as is indicated by the continued downward trend ofthe graph.

The friction recovery test which wa-s made immediately following thecontrolled temperature test at 350 F., and the results of which areexemplied by dotted line graph 20 in Fig. 4, shows a continuous increasein friction as the temperature of the friction element was allowed todecrease from the immediately preceding controlled temperature step to aminimum temperature of 150 F. or less. Hence the final friction duringthis recovery test Was equivalent to the initial friction during thefriction test at a controlled temperature step of 250 F.

The loss of friction or -so-called fade becomes more pronounced in thenext succeeding substantially constant internal lining temperaturefriction test, at 400 F., as shown by the sharp drop in solid line graph21 in Fig. 4. Moreover, the vrecovery friction does not increase to thesame magnitude as inthe preceding steps at 250 F., 300 F., and 350 F.,thus showing that the friction element tested was losing, during thistest, its capacity for` friction recovery after having been subjected toan increase in its internal temperature. Further, the loss of frictionstability in this specimen is further indicated by the continued drop ofdotted line graph 22 in Fig. 4 and which shows the results of thefriction recovery test made upon the specimen immediately following thesubstantially constant internal lining temperature friction test, theresults of which are shown by solid line graph 21 in Fig'. 4. v

' However, by reference to solid line graph 23 in Fig. 4, it will benoted that at the next succeeding substantially constant vinternallining temperature lfriction test at 450 F., the loss in frictionstability in the specimen tested was very pronounced. This is shown bythe fact that the horizontal portion of this graph 23 between the points107.8 and 120.0, represents a marked loss in friction which is shown asa horizontal line because the graph dropsbelow the lower limit of thevabscissae which can b e shown in the drawing. Likewise, in theimmediately succeeding friction vrecovery test, represented by4 dottedline graph 24`in Fig.' 4, the friction element again recovers frictionas the temperature of the element is allowed to decrease, but thefrictional value of the maximum recovery is below the correspondingvalues attainable in the preceding steps at 250 F., 300 F., 350 F., and400 F., respectively.

During the next succeeding internal lining temperature friction test, at500 F., there was a still further pronounced loss of friction in thisspecimen, as shown by solid line graph 25 in Fig. 4, and which isrepresented by a continuous horizontal line, since both decelerationrate extremities of this graph (104.0 and 255.0), and all intermediatepoints, lie below the limits vof theabscissae which can be shown on thedrawing. Likewise, in the next succeeding friction recoveryftest,` theresults of which are shown by dotted line graph 26 in Fig. 4, thefriction element again recovers friction as the temperature of theelement is allowed to decrease, but here again the value of the maximumfriction recovery is below the maximum value the friction element wasable to attain in the preceding steps of 250 F., 300 F., 350 F., and 400F., respectively. These tests show that a friction element employing theparticular prior art bonding agent embodied therein showed a denite anddecided loss in friction when the ingredients of the elements weresubjected to temperatures above 250 F., this loss in friction stabilitydefinitely increasing with each successive increase in the temperatureof the element. It is further shown-that a friction element employingthe particular prior art bonding agent embodied therein which formed thesubject matter of these tests exhibited a decreasing degree of frictionrecovery as the internal temperature of the friction element increased,as is indicated by the continual drop of dotted line graphs 22, 24 and26 in Fig. 4.

Solid line graphs 27, 29, 31, 33, 35 and 37 in Fig. 5 show the resultsof controlled friction internal lining temperatures friction tests at250 F., 300 F., 350 F., 400 F., 450 F., and 500 respectively, uponspecimens of friction elements bonded with the aforesaid preferredsulphurized synthetic highly conjugated isomerized bonding oil ofthepresent invention, namely, the pentaerythrityl ester of highlyconjugated isomerized unsaturated linseed oil fatty acids having 18carbon-atoms in the chain. No special or added friction `controllingagents were employed in these specimens. Dotted line graphs 26, 28, 3,0,32, 34, and 36 in Fig. 5 show the results of friction recovery testsmade upon the same specimens after the corresponding controlledtemperature friction tests, the results of which are shown by solid linegraphs in Fig. 5.

A-s may be seen by reference to the graphs shown in Fig. 5, the frictionelements tested exhibited excellent friction stability and frictionrecovery characteristics as shown by the general horizontal trend orpattern of the broken line graphs, the relatively slight fade" duringthe controlled temperature test at 400 F., as shown by solid line graph33, and the noticeable upward trend vof solid line graphs 35 and 37which exemplify the results of the controlled temperature friction testsat the higher temperatures of 400 F., 450 F., and 500 F., respectively..Similarly the friction recovery tests made following the constanttemperature tests at the higher temperatures of 400 F., 450 F., and 500F.. and the results of which are shown by-graphs 34 `and 36 in Fig.5,.,show similar good friction 25 characteristics in the testedspecimens. More.- over, graphs 32 and 34m Fig.,5. show only a slightdecrease in the maximum friction recovery value below the corresponding`value obtained during the initial friction at the lcontrolledtemperature step at 250 F.

The friction element specimen to which graphs 27, 29, 31, 33, 35 and 37in Fig. 5 relate Wassubjected to successively increasing temperatures offrom 250 F. through 500 F., inclusive, andthe small degree of frictionloss in this specimen is shown by these graphs. Moreover, said frictionelement, embodying a bonding agent of the present invention, exhibiteddenite friction stability as indicated by its frictionrecovery Whensubjected to successive temperatures of from 250 F. through 500 F.,inclusive, as shown by graphs 26, 28, 30, 32, 34 and 36 in Fig. 5.

Likewise, by comparing the graphs shown in Fig. with those in Fig. 4,there will be seen the superior friction characteristics, including themarked improvement instability of friction elements bonded with asulphurized highly conjugated synthetic bonding oil of the presentinvention, namely, the pentaerythrityl esters of highly conjugatedisomerized linseed oil unsaturated fatty acids having 18 carbon atoms inthe chain, over otherwise similar friction elements bonded with acomparable sulphurized bonding oil of the prior art.

Graphs 38 and 39 in Fig. 6 show the friction results of a so-called hotdrum wear test upon friction elements bonded with the same sulphurizedprior art vegetable drying oil as is referred to in the description ofthe graphs Shown in Fig. 4, namely, a so-called purely polymerizedlinseed oil, that is, a heat-polymerized linseed oil containingsubstantially vno oxidized oil. This oil had a viscosity of 600 poisesat atmospheric temperatures and an acid number of about 2.0.

Graphs 40 and 4,1 in Fig. 6 show thefriction results of so-called hotAdrum wear tests upon friction elements otherwise identical to those toWhich graphs 38 and 39 in Fig. 6 relate, except that the `bonding agentwhich Was employed in the friction "element to Which graphs 40 and 41relate was the same sulphurized highly conjugated isomerized syntheticoil which is referred to in the description of the graphs-shown in Fig.5, namely, the pentaerythrityl ester of highly conjugated isomerizedunsaturated linseed oilfatty acids having 18 carbon atoms in the chain`This oil had the same viscosity and acid number aS-the bonding oilemployed in the friction element to Which graphs 38 and 39 in Fig. 6relate.

The'improved friction characteristics of friction elements bonded withthe aforesaid preferred sulphurized highly conjugated isomerizedsynthetic reesteried polyhydric alcohol ester bonding oil of the presentinvention over other Wise similar friction elements bonded with `acomparable prior art bonding oil-referred :to above in the descriptionof the graphs in Fig. 4 andin the description of graphs 38 and 39 inFig. 6 is shown by the comparative lengths of graphs 38, 39, 40

and 41.

Thus graphs 38 and 41 show the average friction of the specimens for 200stops or deceleration, corresponding to braking operations at 530 M; P.H. on an inertia type of dynamometer, ,stopyping at a deceleration rateof 11 ft. per.` second,

per second, with the `temperature of the airin 26 controlled .airstream, and .with .the drum and brake, assembly vtemperature being 4heldata sub stantially constant temperature of 240 F. at thirty miles perhour.

In the case of the M. P. H. test, theresults of which are shown ingraphs39iand41, thefgraphs show theaveragefriction for lstops,continuousbperation, stopping at a. deceleration rate of 1.1ft. persecond, per second, With the temperatureof theatmospheric air inVcontact with the drumandbrakeessembly being held substantiallyconstantat by kmeans of acontrolled airstream, andthe temperature of thedrum and brake assembly being held within limits of from 610 Eto-660 F.

Thus it Will be seenthat the greater length of graphs 38 .and 39 in Fig.6 as compared to graphs 40 and 41 respectively, indicates a markeddecrease in friction, due to heat decomposition of and resulting lack ofstability in the bond, and consequent rapidwear and erratic friction,inthe friction elements bonded with the sulphurized prior .art bondingoil to which graphs 38 and 39 relate as compared to friction elementsbonded with an oil of the present invention and to which graphsAO and 41relate and which exhibited eX- cellent frictiony characteristicsvincluding friction stability and resistance to heat decomposition ofthe `bond of the present invention employed therein.

Graphs 42, 43 and 44 in Fig. 7 show the results of so-calied cold drum`performance tests, at actuatingline pressures rangingfrom to 900 lbs.ateach speedindicated, upon friction elements bonded with the same priorart bonding oil which is identified in the description of the graphsshownin Fig. 4, namely, sulphurized so-called purely polymerized linseedoil, that is, .a sulphurized heat-polymerized liriseed oil containingsubstantially no oxidized oil. Similarlmgraphs 45, 4 6and 47'in Fig. 47show the results of so-called Cold drum performance tests. at actuatingline pressures ranging from v100 .to 900 lbs. at each speed indicated,upon friction elements bonded with theaforesaid highly couille-atedisomerized synthetic reesteried polyhydric alcohol ester b ondngoil ofithepresent invention,v namely, the

,bonding oils is shownbythe relatively shorter lengthofeach of vgraphs45, 46and 47 with the `corresponding I length of graphs 4 2, 43 and 44in Fig. 7.

No special oradded friction controllingorfric- `.tion-.enhancingagentswere employedy in any Aof the friction elements tested, and the resultsof Awhichare.shovvnby the graphsinFigs. 6 and7,

nor in the friction. Slementstested and the. results .of which are shownin the graphs illustrated in Fig.. 8 which will, now be described.

Graphs. 48.arid 49 in Fig.. 8 .show the resultsof L.socalled frictionorfade tests upon friction elements bonded with `the aforesaid prior `art

